1) Field of the Invention
The present invention relates to a method and an apparatus for transferring flexible sheet products stored in a product stack, in particular printed products, according to the preamble of claim 1 and of claim 7.
2) Description of Related Art
EP-A-1 226 083 discloses a method and an apparatus of this type. The apparatus is intended to break down a product stack, in particular a stack of printed products, from below and to deposit the individual products on a belt conveyor for further processing. For this purpose, the apparatus has a plurality of grippers and suction elements, each gripper being assigned a suction element preceding the gripper. The grippers and suction elements are fixed to a carrier wheel. In order to break down the stack, in a pick-up region a suction element grips the product located at the bottom in the product stack in the leading edge region of said product and transfers this product to the following gripper. This gripper holds the product firmly in the leading edge region and, as a result of rotation of the carrier wheel, the product is pulled out of the product stack. As a result of further rotation of the carrier wheel, the product is conveyed into a transfer region, in which it is deposited on a belt conveyor and, after the product has been deposited, it is released by the gripper. In the transfer region, the direction of movement of the gripper is the same as the conveying direction of the belt conveyor.
This known apparatus is afflicted with the disadvantage that the conveying direction of the belt conveyor is coupled with the direction of movement of the grippers in the transfer region. This can be disadvantageous when processing folded printed products. Folded printed products are preferably gripped by the suction element or by the gripper close to the fold or gutter margin, which is consequently located in the leading edge region. As soon as the product has been deposited on the belt conveyor, the fold is once more in front. Processing of the product in such a way that, on the belt conveyor, an open edge opposite the fold forms the leading edge of the printed product and the fold forms the trailing edge of the printed product is not possible with the apparatus disclosed by EP-A-1 226 083.
Furthermore, EP-A-1 226 083 discloses supporting the product stack on a plurality of freely rotatable rolls, the rolls in the pick-up region moving from the leading edge region to the trailing edge region. As a result of gripping the leading edge region of the lowest product and pulling this edge region down through between two adjacent rolls by means of the suction element, the lowest product can be separated gently from the product stack.
The rolls are arranged on two conveyor elements and are located directly underneath the product stack in a horizontal plane. The rolls are arranged pivotably on the conveying elements such that, in a region directly underneath the product stack, the rolls are aligned in parallel at regular intervals and, outside this region, in a plane in which the conveying element is located, and are pivoted away upright.
A further, similar apparatus for the breakdown of a product stack is disclosed by EP-A 1 254 855. A product stack is once more located on freely rotatable rolls. The rolls are arranged pivotably on the conveying wheel such that, in a region under the product stack, they are aligned parallel to the axis of rotation of the conveying wheel and, outside this region, in a plane in which the conveying wheel is located, are pivoted and aligned at least approximately tangentially.